Process for the recovery of rare earth metals from permanent magnets

ABSTRACT

Systems and methods for recovering rare earth metals from rare earth metal-containing magnets includes fragmenting or commutating the magnets, contacting the commutated magnets with a mixture of low molecular weight carboxylic acids such as formic acid and water, and removing or extracting non-rare earth metal carboxylate phases such as an iron carboxylate (formate) phase from a rare earth metal carboxylate (formate) phase, using a solvent such as water.

RELATED APPLICATIONS

The present patent application is a divisional of U.S. patentapplication Ser. No. 15/743,463, filed Jan. 10, 2018, which is a U.S.National Stage Application filed under 35 U.S.C § 371(a) ofInternational Application No. PCT/US2016/041685, filed Jul. 11, 2016,which claims priority to and the benefit of U.S. Provisional PatentApplication No. 62/191,238 filed Jul. 10, 2015 (10 Jul. 2015). Theentire contents of each of the foregoing applications are herebyincorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

Embodiments of the present invention relate to systems and methods forrecycling rare earth elements from end-of use products containing rareearth magnets.

More particularly, embodiments of this invention relates to systems andmethods for recycling rare earth elements from end-of use productscontaining rare earth magnets, especially neodymium-iron-boron (NdFeB)magnets, where the methods include the steps of optionally fragmentingor commutating the magnets, contacting the commutated magnets with amixture of formic acid and water to form rare earth metal (REM) formateprecipitates (REM(HCOO)₃), separating the filtrate, which is impregnatedwith non-rare earth metal (NREM) components including iron formates(Fe(HCOO)₂) and borate/boric acid (BO₃ ⁻/H₃BO₃) by a solid-liquidseparation, and purifying the precipitated REM(HCOO)₃ by washing withexcess water, and calcining the recovered REM(HCOO)₃ products to rareearth oxides (REM₂O₃ and REM₆O₁₁).

2. Description of the Related Art

NdFeB permanent magnets are fundamental components for various cleanenergy and high technology applications. NdFeB magnets are used, forexample, in electric motors, wind turbines, missile guidance systems,hard drives, speakers, and many other existing and new technologies. Therare earth metals (REMs) in NdFeB magnets may also include, but notlimited to, combinations of neodymium (Nd), praseodymium (Pr),Dysprosium (Dy), and Terbium (Tb). In some context Gadolinium (Gd) andSamarium (Sm) may also present. Nd and Dy, the primary rare earthcomponents of NdFeB magnets are classified as two of the most criticalrare earth elements in terms of supply risk and importance to advancetechnological fields by the U.S. Department of Energy.¹ In 2015, globaldemand for neodymium and dysprosium is projected to rise to 45,500 MTwith an imminent supply shortage of 34,700 MT global production.²

Currently, the primary source for Nd and Dy are from rare earth elementmining companies. The global rare earth supply, however, has not beenincreasing as quickly as the rise in demand due to long lead times,trade policies, environmental concerns, and other factors effecting rareearth mining. Thus, recycling of NdFeB magnets to recover Nd and Dy isconsidered an attractive approach to mitigate the global rare earthsupply shortage. Although commercial scale waste NdFeB magnets recyclingefforts are almost non-existent to date, several research projects onNdFeB magnets recycling have been reported.

Prior art and literature on methods for rare earth magnet recyclingmostly comprise of hydrometallurgical methods³ and pyrometallurgicalmethods.⁴ Recently, hydrogen decrepitation (HD) methods,⁵ gas-phaseextraction methods,⁶ and hydrothermal methods⁷ were proposed asalternate approaches. The different recycling routes have, however,different advantages and disadvantages, described in greater detailelsewhere.⁸

Hydrometallurgical processes are by far the most common and main methodsfor recycling rare earths. Hydrometallurgical methods are employedmostly in commercial processes of rare earth recovery from primarymineral ores or scrap generated during the magnets manufacturing. Atypical hydrometallurgical rare earth recovery process involves strongacid digestion steps which use hydrochloric acid, nitric acid orsulfuric acid to leach the rare earths, followed by a solvent extractionof the rare earth components or by a precipitation of the rare earthcomponents using a suitable precipitating agent such as oxalate,fluoride or double salt sulfate.

The use of strong acids and the large amounts of chemicals required inhydrometallurgical processes have significant adverse environmental andeconomic impacts. The processes result in large amounts of liquid acidwaste which causes significant waste disposal issues. During theextraction step, an excess amount, about 10 times or more of thestoichiometric amount of acid is used to enhance the stripping effect.Some of the chemicals used in the recovery processes such as fluorides,nitrates and sulfates, generate toxic, strongly oxidizing orair-polluting gases such as HF, NO₂, SO₂ and H₂S. From the economicperspective, obtaining high-purity single rare earth products is acommon problem. In current processes co-precipitation of contaminantsalong with the rare earth phases is commonly observed. Most of theseco-precipitated phases are not easily removable. Several other stepssuch as re-dissolution and re-precipitation are needed to purify therare earth phases. The overall process is complex and multi-stepresulting in longer lead times, low yields and high production costs. Asa consequence it is hard to implement such methods in industrial rareearth recycling processes.

The methods disclosed in the prior art for NdFeB magnet recycling aremainly the methods for rare earth recovery from the pre-consumerproduction scrap or sludge. The end-of-use magnet scrap recycling isminimally researched or disclosed in the prior art. Thus, the effect ofother waste materials such as the protective coating of the magnets onthe recycling process is not well known. In an ideal approach, the rareearth elements need to be selectively recovered, leaving behind all theother waste materials. Given the fact that protective coating consistsof nickel and copper metals, it is nearly impossible to avoid thesemetal ions dissolving in the leaching solution. This makes the recyclingof post-consumer NdFeB magnets more complex given the need to avoid allother elements including Fe, B, Ni, and Cu in the final rare earthproduct.

In a previous patent application U.S. Pat. No. 9,376,735B2 issued Jun.28, 2016 entitled “Methods and Systems for Recovering Rare EarthElements” to Jacobson and Samarasekere, we disclosed methods and systemsfor recovering or extracting rare earth elements under mild conditionsusing a rare earth element crystallization approach. We used acrystallization medium under solvothermal conditions sufficient to formrare earth element crystals capable of gravity separation andpurification. This previous invention used formamide with the additionof small amounts of formic acid and water as the dissolution andcrystallization medium. Several other metals for rare earth metalrecovery have been proposed such as US20110023660A1 published Feb. 3,2011 entitled Method and Apparatus for Recovery of Rare Earth Element,U.S. Ser. No. 00/542,9724A published Jul. 4, 1995 entitled NeodymiumRecovery Process, and U.S. Pat. No. 6,533,837B1 issued Mar. 18, 2003entitled Method of Recovering and Recycling Magnetic Powder from RareEarth Bond Magnet.

While several methods have been represented above, there is asignificant need for better approaches for the efficient, economical andmore environmental friendly recycling of rare earth elements.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide methods for recovering rareearth metals (REMs) from waste magnets comprising contacting a rareearth metal-containing magnet material with a reactant compositionincluding a low molecular weight carboxylic acid and water underreaction conditions sufficient to dissolve or extract and concurrentlyprecipitate rare earth metals from the rare earth metal-containingmagnet material forming a precipitate including rare earth metalcarboxylates and non-rare earth metal components, and removing thenon-rare earth metal components from the rare earth metal carboxylateswith water to form a purified rare earth metal carboxylate product.

Embodiments of the present invention provide methods for recovering rareearth metals (REMs) from rare earth containing magnets, where themethods include a reaction step, where rare earth metal containingmagnets are reacted with a formic acid/water mixture to dissolve rareearth metals and non-rare earth metals from the magnets forming rareearth metal (REM) formates and non-rare earth metal (NREM) formatesand/or other NREM components. The REM formate precipitates, while theNREM formates and/or other NREM components are more soluble and eitherremain in solution or form part of the precipitate. The methods alsoinclude filtrating the precipitates from the reaction mixture andwashing the precipitate with a solvent to extract any remaining non-rareearth metal formates in the precipitate leaving a purer rare earthformate product, where the solvent is characterized in that the NREMformates and/or other NREM components are more soluble in the solventthan the REM formates. The methods of this invention are economical dueto the minimum number of process steps and minimum chemical usage. Asthe reaction involves a metal reacting with an acid, the reactiongenerates a stoichiometric amount of hydrogen gas. The hydrogen gas maybe disposed of by controlled burning in a combustion unit, feed to ahydrogen fuel cell for energy production, used in a hydrogenationreaction, or captured and stored for subsequent use. Thus, in certainembodiments, the hydrogen gas may be used as a fuel source to supplysome or all of the energy needed to heat the reaction vessel.

The methods of this invention were successfully tested using NdFeBmagnets recovered from hard disk drives, but may be used with any typeof REM containing magnet products. The methods of this invention may beperformed with or without any pretreatment steps, such asdemagnetization or protective coating removal. Thus, the methods of thisinvention are simpler, less environmentally destructive or disruptive,and/or are a more economical approach for recovering rare earth elementsfrom the REM containing magnets such as NdFeB magnets. The experimentshave shown that the methods of this invention are capable of recoveringat least 75% of the REMs present in the REM containing magnet materials.In certain embodiments, the recovery rate is as least 80% of the REM spresent in the REM containing magnet materials. In other embodiments,the recovery rate is as least 85% of the REMs present in the REMcontaining magnet materials. In other embodiments, the recovery rate isas least 90% of the REMs present in the REM containing magnet materials.In other embodiments, the recovery rate is as least 95% of the REMspresent in the REM containing magnet materials. Chemical analysis of thefinal rare earth product phases has shown that the methods of thisinvention are capable of recovering REM formates in greater than 90%purity, for example about 99% purity relative to the NREMs.

Embodiments of the present invention provide systems comprising areaction vessel including a rare earth metal containing-magnet materialinput connect to a rare earth metal containing-magnet material source, alow molecular weight carboxylic acid input connected to a low molecularweight carboxylic acid source, a water input connected to a watersource, a waste liquid outlet connected to a waste liquid receiver and arare earth metal product outlet connected to a rare earth metal productreceiver, where an amount of the rare earth metal containing-magnetmaterial, the low molecular weight carboxylic acid and the water areadded to the reaction vessel to form a reaction mixture and the reactionmixture is held under reaction conditions sufficient to dissolve orextract the rare earth metals to form rare earth metal carboxylatesalong with non-rare earth metal carboxylate hydrates that precipitateout of the reaction mixture, and a separating vessel to separate theprecipitate from the liquid and to wash the precipitate with a solventto remove the non-rare earth metal carboxylate hydrates to form apurified rare earth carboxylate product.

Embodiments of the present invention provide systems for recovering REMsfrom REM containing magnet materials, where the systems include areaction subsystem, a separation subsystem, and extraction subsystem.The reaction subsystem includes at least one reaction vessel forcontacting a REM containing magnet materials with an aqueous formic acidsolution or a mixtures of formic acid and water as a reactantcomposition to dissolve and/or extract the REMs contained in the REMcontaining magnet materials. The separation subsystem includes at leastone separation vessel for removing a precipitate from a liquid. Theextraction subsystem includes at least one extraction vessel forremoving or extracting residual NREM formates from REM formates. Thesystems and methods operate on the basis of the differential solubilityof the REM formates compared to the NREM formates in the solvent used toremove or extract residual NREM formates from the precipitate resultingin a substantially pure REM formate product. In certain cases, themagnets are coated with a protective coating, typically a copper nickelcoating comprising either layers of Cu and Ni or a Cu/Ni alloy. Thesecoatings minimally dissolve in the formic acid/water mixture and mostremain behind in the precipitate and do not appear to interfere with theextraction and/or dissolution process, but the coating pieces in theprecipitate may be readily removed magnetically.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the followingdetailed description together with the appended illustrative drawings inwhich like elements are numbered the same:

FIGS. 1A and 1B depict a first embodiment of a system osf thisinvention.

FIG. 1 depicts a second embodiment of a system of this invention.

FIG. 2 depicts a third embodiment of a system of this invention.

FIG. 3 depicts a fourth embodiment of a method of this invention.

FIG. 4 depicts powder X-ray patterns (PXRD) of (a) as synthesized solidproduct of the reaction. Solid phase consists of a mixture ofREM(HCOO)₃, where REM is a rare earth metal, and Fe(HCOO)₂.2H₂O; (b)simulated PXRD pattern of Fe(HCOO)₂.2H₂O; (c) simulated PXRD pattern ofNd(HCOO)₃; and (d) nearly-pure REM(HCOO)₃ phase after Fe(HCOO)₂.2H₂Oremoval.

FIGS. 6a &b depicts SEM micrographs and EDX analysis of; (a)as-synthesized rare REM(HCOO)₃ crystals; (b) a rare earth metal oxideproduct after annealing.

DEFINITIONS OF TERM USED IN THE INVENTION

The following definitions are provided in order to aid those skilled inthe art in understanding the detailed description of the presentinvention.

The term _about_ means that the value is within about 10% of theindicated value. In certain embodiments, the value is within about 5% ofthe indicated value. In certain embodiments, the value is within about2.5% of the indicated value. In certain embodiments, the value is withinabout 1% of the indicated value.

The term _substantially_ means that the value is within about 5% of theindicated value. In certain embodiments, the value is within about 2.5%of the indicated value. In certain embodiments, the value is withinabout 1% of the indicated value. In certain embodiments, the value iswithin about 0.5% of the indicated value. In certain embodiments, thevalue is within about 0.1% of the indicated value.

The term “REM” means a rare earth metal and REMs means rare earth metalsselected from the group consisting of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb,Dy, Ho, Er, Tm, Yb, Lu, Y, and/or Sc.

The term “w/w” means weight of magnet materials per weight of dissolvingacid or weight of magnet materials to weight of water or weight ofdissolving acid to weight of water.

The term “w/v” means weight of magnet material per volume of solvent.

The term “v/v” means volume of solute per volume of solvent.

The term “w/v ratio” means ratio of weight of magnet material to volumeof dissolving solvent system.

The term “v/v ratio” means volume of solute to volume of solvent, herevolume of water to dissolving acid.

The term “wt. %” means weight percent.

The term “vol. %” means volume percent.

DETAILED DESCRIPTION OF THE INVENTION

The inventors have found that the present systems and methods overcomethe problems discussed above producing an efficient approach to recoverrare earths from of rare earth metal (REM) containing magnet materialssuch as NdFeB waste magnet materials using an aqueous carboxylic acidsolution as the only chemical reagent for dissolving out the REMs fromthe magnets, with or without prior pre-treatment, to form a precipitatefrom which residual non-rare earth metal (NREM) components are removedby solvent washing or extraction leaving a purer REM product. In thepresent invention, post-consumed NdFeB waste magnets were directlycontacted and/or reacted with an aqueous acid solution such as anaqueous formic acid solution. The REMs were then recovered as insolubleREM caboxylates such as REM formates of the general formula REM(HCOO)₃.Throughout the processes, the carboxylic acid acts both as a leachingagent and a precipitating agent. The extraction and/or dissolution ofREMs from the magnets and the precipitation of the REM carboxylatesoccur concurrently and/or simultaneously, thus the process may beclassified as a one-pot synthetic approach to REM recovery from REMcontaining magnet materials. One especially effective carboxylic acid isformic acid also the smallest carboxylic acid. Formic acid has a lowtoxicity and a minimal environmental impact. By using stoichiometricamounts of formic acid to react with the REMs in the magnet materials,the amount of acid waste generated from the processes may be reduced,minimized, substantially eliminated, or completely eliminated. Besidesthe formation of REM and non-rare earth metal (NREM) carboxylates suchas formates of iron, nickel or other transitions metals, andborates/boric acid the reaction generates stoichiometric amount ofhydrogen gas (H₂).

In the case of the carboxylic acid being formic acid, several differentREM formates have been described in the literature. Simple anhydrous REMcompounds having general formula REM(HCOO)₃, have been known for manyyears and are well characterized structurally.⁹ The compounds have aneutral framework structure composed of REM ions coordinated by theoxygen atoms of the formate ligands. The REM³⁺ ions are coordinated bynine oxygen atoms in a tricapped trigonal prismatic geometry. The oxygenatoms of the formate ligand differ; one forms μ²-bridges betweenneighboring REM³⁺ ions, while the second is mono-coordinating. The spacegroup is non-centric.

The reactant compositions of the present invention comprise an aqueoussolution of formic acid or other low molecular weight carboxylic acid.The reaction is characterized by the following reactions of formic acidand REMs:

REM+3RCOOH→REM(RCOO)₃+(3/2)H₂

NREM+nRCOOH→NREM(RCOO)n+(n/2)H₂

where REM is a rare earth metal, R is a hydrogen atom or an alkyl grouphaving between 1 and 3 carbon atoms, and n is an integer having valuebetween 2 and 3. In certain embodiments, the REM is Nd and the NREM isFe and R is a hydrogen atom and n is 2. As the reaction generationstoichiometric amount of hydrogen gas, the hydrogen gas may be disposedof by controlled burning in a combustion unit, feed to a hydrogen fuelcell for energy production, used in hydrogenation reaction, or capturedand stored for subsequent use. Thus, in certain embodiments, thehydrogen gas may be used as a fuel source to supply some or all of theenergy needed to heat the reaction to vessel.

The reaction mixture may be characterized by two ratio: a ratio ofmagnet material to formic acid and a ratio of formic acid to water or bya single ratio of magnet material to formic acid to water. These ratioare best expressed on a w/w basis. The stoichiometric reactant ratiosmay be calculated by assuming an irreversible reaction. Based on thebalanced equation, the theoretical ratio of magnet materials to formicacid may be calculated as 1:1.44 w/w. Based on the solubility data ofFe(HCOO)₂.2H₂O at 25° C., the theoretical amount of water required todissolve all the Fe(HCOO)₂.2H₂O can be calculated as 1:30 w/w magnetmaterials to water. Thus, the ratio of magnetic material to formic acidto water is 1:1.44:30 w/w. In general operation, the ratio of magnetmaterial to formic acid to water is between about 1:1:20 w/w to about1:2:50 w/w. In other embodiments, the magnet material to formic acid towater ratio is between about 1:1.2:20 w/w and about 1:1.8:50 w/w. Inother embodiments, the magnet material to formic acid to water ratio isbetween about 1:1.3:20 w/w and about 1:1.6:50 w/w. In other embodiments,the magnet material to formic acid to water ratio is between about1:1.4:20 w/w and about 1:1.5:50 w/w. In other embodiments, the magnetmaterial to formic acid to water ratio is between about 1:1.4:20 w/w andabout 1:1.5:40 w/w.

Reaction Conditions of the Invention

The parameters or reaction conditions used in the examples of thereaction processes of this invention including at least reactiontemperature, reaction pressure, reaction time, and stirring rate. Ingeneral, the reaction temperature is between about 25° C. and about 120°C. In certain embodiments, the reaction temperature may be any discretetemperature in the range between about 25° C. and about 120° C. In otherembodiments, the reaction temperature may be selected from the group ofselected from 25° C., 50° C., 75° C., 100° C., and 120° C. In general,the reaction pressure is between about 1 atmosphere and about 5atmospheres. In other embodiments, the reaction pressure is betweenabout 1 atmosphere and 2 atmospheres. In other embodiments, the pressureis ambient pressure. In general, the reaction time is up to 24 hours ormore. In certain embodiments, the reaction time is between about 3 hoursand 24 hours. In other embodiments, the reaction time is any discretetime period in the range between 3 hours and 24 hours. In otherembodiments, the reaction time is selected from the group consisting of3 hours, 6 hours, 9 hours, 12 hours, 15 hours, 18 hours, 21 hours, and24 hours. In general, the rate of stirring is up to 500 rpm or more. Inother embodiments, the stirring rate is between about 100 rpm and 500rpm. In other embodiments, the reaction time is any discrete stirringrate in the range between 100 rpm and 500 rpm. In other embodiments, thestirring rate is selected from the group consisting of 100 rpm, 150 rpm,200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, and 500 rpm.

Once the rare earth metals are separated as REM(HCOO)₃ product, theprecipitate may be converted to economically valuable mixed rare earthoxides through a calcination step. The calcination may be performed byheating REM(HCOO)₃ product to a calcination temperature in the rangebetween about 750° C. and about 1,000° C. for a calcination time betweenabout 3 hours and about 5 hours.

It should also be noted that the invention may also be applied to therecovery of REMs from other REM magnet materials including, but notlimited to, Samarium-Cobalt (Sm—Co) magnet materials.

Suitable Reagents and Components of the Invention

Suitable reagent used for this processes of this invention include lowmolecular weight carboxylic acids of the general formula RCOOH orR—C(O)—OH, where R is H or an alkyl group having between 1 and 3 carbonatoms. Exemplary examples include, without limitation, formic acid(HCOOH or H—C(O)—OH) representing the smallest member of the carboxylicacids useful in the present invention, acetic acid (CH₃COOH orCH₃—C(O)—OH), propanoic acid (CH₃CH₂COOH or CH₃CH₂—C(O)—OH), other lowmolecular weight carboxylic acids, or mixtures and combinations thereof.Formic acid is a weak organic acid and is considered to be a reagenthaving low toxicity and environmentally friendly solvent due to its lowenvironmental impact. Due to its relatively high hydrogen content,formic acid has been proposed as a valuable, safe and economicalhydrogen carrier. Formic acid may be catalytically decomposed to yieldhydrogen and carbon dioxide, while in the present invention, thereaction are controlled to yield metal formates and hydrogen gas. Underproper reaction conditions formic acid ionizes to formate anions (HCO₂—or H—C(O)—O⁻) and hydrogen ions (H⁺). In this invention, we disclose theuse of formic acid as an effective reagent for the recovery of rareearth components from magnets such as NdFeB magnets as rare earthformates of the structure (REM(HCOO)₃).

Suitable rare earth metals (REMs) to be extracted by the methods andsystems of this invention include, without limitation, Lanthanum (La),Cerium (Ce), praseodymium (Pr), neodymium (Nd), Promethium (Pm),Samarium (Sm), Europium (Eu), Gadolinium (Gd), Terbium (Tb), Dysprosium(Dy), Holmium (Ho), Erbium (Er), Thulium (Tm), Ytterbium (Yb), Lutetium(Lu), and mixtures or combinations thereof.

Suitable non-rare earth metals or elements (NREMs) to be extracted bythe methods and systems of this invention include, without limitation,iron (Fe), nickel (Ni), copper (Cu), boron (B) other transitions metalsgenerally associated with materials that include REMs, and mixtures orcombinations thereof.

DETAILED DESCRIPTION OF THE SYSTEM AND METHOD FIGURES First Embodiment

Referring now to FIG. 1A, a first embodiment of system of thisinvention, generally 100, is shown to include a heated reaction vessel102 including a motor 104 and a paddle stirrer 106. The reaction vessel102 also includes a REM containing magnet material inlet 108, a waterinlet 110 and a formic acid inlet 112. The reaction vessel 102 alsoincludes a gas outlet 114, a waste liquid outlet 116 and a REM productoutlet 118.

The system 100 also includes a REM containing magnet material sourcevessel 120 having a REM containing magnet material outlet 122. Theoutlet 122 is connected to the inlet 108 via a REM containing magnetmaterial conduit 134 having a REM containing magnet material conduitvalve 136.

The system 100 also includes a water source vessel 138 having a wateroutlet 140. The water outlet 140 is connected to the water inlet 110 viaa water conduit 142 having a water conduit valve 144. The system 100also includes a formic acid source vessel 146 having a formic acidoutlet 148. The formic acid outlet 148 is connected to the formic acidinlet 112 via a formic acid conduit 150 including a formic acid conduitvalve 152.

The system 100 also includes a hydrogen gas bubbler 154 having ahydrogen gas inlet 156 and a hydrogen gas outlet 158, where the gasoutlet 114 is connected to the hydrogen gas inlet 156 via a hydrogen gasconduit 160 having a hydrogen gas valve 161. The system 100 alsoincludes a hydrogen gas utilization or storage unit 162 having ahydrogen gas inlet 164 connected to the hydrogen gas outlet 158 via asecond hydrogen gas conduit 166. In certain embodiments, the hydrogengas utilization or storage unit 164 may be a combustor, where the heatproduced may be used to heat the reaction vessel 102 to a desiredelevated temperature. In other embodiments, the hydrogen gas utilizationor storage unit 162 may be a hydrogen fuel cell for generatingelectrical power that may be used to heat the reaction vessel 102 or topower the reaction controllers and other electrical equipment associatedwith the systems. In other embodiments, the hydrogen gas utilization orstorage unit 164 may be a hydrogen gas storage vessel, where thehydrogen gas is stored for latter use such as combustion in combustorsor fuel cells or in hydrogenation reactions or in any other process thatuses hydrogen gas as a reagent.

The system 100 also includes a waste liquid vessel 168 having a wasteliquid inlet 170, where the waste liquid outlet 116 is connected to thewaste liquid inlet 170 via a waste liquid conduit 172 having a wasteliquid conduit valve 174. The system 100 also includes a rare earthproduct vessel 176 having a rare earth product inlet 178, where the rareearth product outlet 118 is connected to the rare earth product inlet178 via a rare earth conduit 180 having a rare earth conduit valve 182.

The system 100 operates as follows. Rare earth containing HDD magnetsare loaded into the vessel 120. The valve 132 is opened and the magnetsenter the commutating unit 124, where the magnets are commutated into aparticulate magnet input material. The commutating may be accomplishedby grinding, cryogenic grinding, pressure fracturing, shredding, anyother commutating technique or mixtures and combinations thereof. Thevalve 136 is opened and the particulate magnetic input material issupplied to the reactor vessel 102. Once a desired amount of the inputmaterial is added to the reactor 102, the valve 136 is closed and amixture of water and formic acid is added to the reactor 102, where therelative amount of water and formic acid are controlled by the valves144 and 152. Once the designated amount of water and formic acid areadded, the valves 144 and 152 are closed. The reaction vessel 102 isstirred and maintained at a temperature of about 100° C. Gas evolvedduring the reaction exits the reaction vessel 102 into the hydrogen gasbubbler 154. After the desired reaction time, waste liquid is withdrawnfrom the reaction vessel 102, by opening the valve 174 into the wasteliquid vessel 168. After the waste liquid is removed, the valve 174 isclosed. The solids in the reaction vessel 102 are washed with water byopen the water valve 144 until substantially all or all non-rare earthprecipitate is dissolved by the added water. Once the non-rare earthprecipitate has been dissolved away, the water valve 144 is closed andthe rare earth product valve 182 is opened transferring the product intothe product vessel 176. Thus, the major part of the reaction occurs inthe reaction vessel 102. The generated hydrogen gas proceeds through thebubbler 154 and into the hydrogen gas utilization or storage vessel 162.

In certain embodiments, the reaction vessel 102 will be purged with aninert gas such as nitrogen, argon, methane, hydrogen, or mixtures andcombinations thereof to remove unwanted oxygen gas to minimize metaloxidation especially iron oxidation to the ferric oxidation state. Thus,the reaction vessel 102 may further includes an inert gas inlet 184 anda purge gas outlet 186. The reactor vessel 102 also includes an inertgas vessel 188 having an inert gas outlet 190 connected to the inert gasinlet 184 via an inert gas conduit 192 having an inert gas valve 193.The inert gas fed into the reactor vessel 102 passes through thereaction medium removing unwanted gases and exits the reactor vessel 102through the purge outlet 186 through a purge conduit 194 having a purgevalve 196 into a purge vent 198 having an inlet 199. The inert gas maybe used at different stages of the reaction to purge gases from thereaction medium.

Second Embodiment

Referring now to FIG. 1B, a first embodiment of system of thisinvention, generally 100, is shown to include a heated reaction vessel102 including a motor 104 and a paddle stirrer 106. The reaction vessel102 also includes a particulate REM containing magnet material inlet108, a water inlet 110 and a formic acid inlet 112. The reaction vessel102 also includes a gas outlet 114, a waste liquid outlet 116 and a REMproduct outlet 118.

The system 100 also includes a REM containing magnet material sourcevessel 120 having a REM containing magnet material outlet 122. Thesystem 100 also includes a commutating unit 124 having a REM containingmagnet material inlet 126 and a particulate REM containing magnetmaterial outlet 128. The REM containing magnet material outlet 122 isconnected to the magnet inlet 126 via a magnet conduit 130 having amagnet conduit valve 132. The particulate magnet outlet 128 is connectedto the particulate magnet inlet 108 via a particulate magnet conduit 134having a particulate magnet conduit valve 136.

The system 100 also includes a water source vessel 138 having a wateroutlet 140. The water outlet 140 is connected to the water inlet 110 viaa water conduit 142 having a water conduit valve 144. The system 100also includes a formic acid source vessel 146 having a formic acidoutlet 148. The formic acid outlet 148 is connected to the formic acidinlet 112 via a formic acid conduit 150 including a formic acid conduitvalve 152.

The system 100 also includes a hydrogen gas bubbler 154 having ahydrogen gas inlet 156 and a hydrogen gas outlet 158, where the gasoutlet 114 is connected to the hydrogen gas inlet 156 via a hydrogen gasconduit having a hydrogen gas valve 161. The system 100 also includes ahydrogen gas utilization or storage unit 162 having a hydrogen gas inlet164 connected to the hydrogen gas outlet 158 via a second hydrogen gasconduit 166. In certain embodiments, the hydrogen gas utilization orstorage unit 162 may be a combustor, where the heat produced may be usedto heat the reaction vessel 102 to a desired elevated temperature. Inother embodiments, the hydrogen gas utilization or storage unit 162 maybe a hydrogen fuel cell for generating electrical power that may be usedto heat the reaction vessel 102 or to power the reaction controllers andother electrical equipment associated with the systems. In otherembodiments, the hydrogen gas utilization or storage unit 162 may be ahydrogen gas storage vessel, where the hydrogen gas is stored for latteruse such as combustion in combustors or fuel cells or in hydrogenationreactions or in any other process that uses hydrogen gas as a reagent.

The system 100 also includes a waste liquid vessel reaction vessel 168having a waste liquid inlet 170, where the waste liquid outlet 116 isconnected to the waste liquid inlet 170 via a waste liquid conduit 172having a waste liquid conduit valve 174. The system 100 also includes arare earth product vessel 176 having a rare earth product inlet 178,where the rare earth product outlet 118 is connected to the rare earthproduct inlet 178 via a rare earth conduit 180 having a rare earthconduit valve 182.

The system 100 operates as follows. REM containing HDD magnets areloaded into the vessel 120. The valve 132 is opened and the magnetsenter the commutating unit 124, where the magnets are commutated into aparticulate magnet input material. The commutating may be accomplishedby grinding, cryogenic grinding, pressure fracturing, shredding, anyother commutating technique or mixtures and combinations thereof. Thevalve 136 is opened and the particulate magnetic input material issupplied to the reactor vessel 102. Once a desired amount of the inputmaterial is added to the reactor 102, the valve 136 is closed and amixture of water and formic acid is added to the reactor 102, where therelative amount of water and formic acid are controlled by the valves144 and 152. Once the designated amount of water and formic acid areadded, the valves 144 and 152 are closed. The reaction vessel 102 isstirred and maintained at a temperature of about 100° C. Gas evolvedduring the reaction exits the reaction vessel 102 into the hydrogen gasbubbler 154. After the desired reaction time, waste liquid is withdrawnfrom the reaction vessel 102, by opening the valve 174 into the wasteliquid vessel 168. After the waste liquid is removed, the valve 174 isclosed. The solids in the reaction vessel 102 are washed with water byopen the water valve 144 until substantially all or all non-rare earthprecipitate is dissolved by the added water. Once the non-rare earthprecipitate has been dissolved away, the water valve 144 is closed andthe rare earth product valve 182 is opened transferring the product intothe product vessel 176. Thus, the major part of the reaction occurs inthe reaction vessel 102. The generated hydrogen gas proceeds through thebubbler 154 and into the hydrogen gas utilization or storage vessel 162.

In certain embodiments, the reaction vessel 102 will be purged with aninert gas such as nitrogen, argon, methane, hydrogen, or mixtures andcombinations thereof to remove unwanted oxygen gas to minimize metaloxidation especially iron oxidation to the ferric oxidation state. Thus,the reaction vessel 102 may further includes an inert gas inlet 184 anda purge gas outlet 186. The reactor vessel 102 also includes an inertgas vessel 188 having an inert gas outlet 190 connected to the inert gasinlet 184 via an inert gas conduit 192 having an inert gas valve 193.The inert gas fed into the reactor vessel 102 passes through thereaction medium removing unwanted gases and exits the reactor vessel 102through the purge outlet 186 through a purge conduit 194 having a purgevalve 196 into a purge vent 198 having an inlet 199. The inert gas maybe used at different stages of the reaction to purge gases from thereaction medium.

Third Embodiment

Referring now to FIG. 2, a first embodiment of system of this invention,generally 200, is shown to include a reaction subsystem 202, aseparation subsystem 250, and an extraction subsystem 270.

Reaction Subsystem

The reaction subsystem 202 includes a single reaction vessel 204, a REMcontaining magnet material source vessel 206, a formic acid sourcevessel 208, and a water source vessel 210. The magnet material sourcevessel 206 is connected to the reaction vessel 204 via a magnet materialconduit 212 having a magnet material valve 214. The formic acid sourcevessel 208 is connected to the reaction vessel 204 via a formic aidconduit 216 having a formic acid valve 218. The water source vessel 210is connected to the reaction vessel 204 via a water conduit 220 having awater valve 222. The reaction vessel 204 also includes a hydrogen gasutilization unit 224 connected to the reaction vessel 204 via a hydrogengas conduit 226 having a hydrogen gas valve 228. The reaction vessel 204also includes an inert gas source 230 connected to the reaction vessel204 via an inert gas conduit 232 having an inert gas valve 234. Thereaction vessel 204 also includes a purge gas vent 236 connected to thereaction vessel 204 via a purge gas conduit 238 having a purge gas valve240. The reaction vessel 204 also includes a reaction mixture conduit242 having a reaction mixture valve 244.

Separation Subsystem

The separation subsystem 250 is shown here to comprise a singleseparation vessel 252 and a liquid receiving vessel 254. The reactionmixture conduit 242 connects the reaction vessel 204 and the separationvessel 252 and is used to transport the reaction mixture from thereaction vessel 204 to the separation vessel 252. The separation vessel252 is connected to the liquid receiving vessel 254 via a liquid conduit256 having a liquid valve 258. The separation vessel 252 also includes asolids conduit 260 having a solids valve 262.

Extraction Subsystem

The extraction subsystem 270 is shown here to comprise a singleextraction vessel 272, a solvent source vessel 274, a liquid vessel 276,and a product vessel 278. The solids conduit 260 connects the separationvessel 252 and the extraction vessel 272 and is used to transport thesolids from the separation vessel 252 to the extraction vessel 272. Theseparation vessel 272 is connected to the solvent source vessel 274 viaa solvent conduit 280 having a solvent valve 282. The separation vessel272 is also connected to the liquid vessel 276 via a liquid conduit 284having a liquid valve 286. The separation vessel 272 is also connectedto the product vessel 274 via a product conduit 288 having a productvalve 290.

Fourth Embodiment

Referring now to FIG. 3, a second embodiment of system of thisinvention, generally 300, is shown to include a reaction subsystem 302,a separation subsystem 346, an extraction subsystem 350, and a recoveryand recycle subsystem 380.

Reaction Subsystem

The reaction subsystem 302 includes a single reaction vessel 304, amagnet source vessel 306, a formic acid source vessel 308, and a watersource vessel 310. The magnet source vessel 306 is connected to thereaction vessel 304 via a magnet conduit 312 having a magnet valve 314.The formic acid source vessel 308 is connected to the reaction vessel304 via a formic aid conduit 316 having a formic acid valve 318. Thewater source vessel 310 is connected to the reaction vessel 304 via awater conduit 320 having a water valve 322. The reaction vessel 304 alsoincludes a hydrogen gas utilization unit 324 connected to the reactionvessel 304 via a hydrogen gas conduit 326 having a hydrogen gas valve328. The reaction vessel 304 also includes an inert gas source 330connected to the reaction vessel 304 via an inert gas conduit 332 havingan inert gas valve 334. The reaction vessel 304 also includes a purgegas vent 336 connected to the reaction vessel 304 via a purge gasconduit 338 having a purge gas valve 340. The reaction vessel 304 alsoincludes a reaction mixture conduit 342 having a reaction mixture valve344.

Separation Subsystem

The separation subsystem 346 is shown here to comprise a singleseparation vessel 348 and a liquid receiving vessel 350. The reactionmixture conduit 342 connects the reaction vessel 304 and the separationvessel 348 and is used to transport the reaction mixture from thereaction vessel 304 to the separation vessel 348. The separation vessel352 is connected to the liquid receiving vessel 350 via a liquid conduit352 having a liquid valve 354. The separation vessel 352 also includes asolids conduit 356 having a solids valve 358.

Extraction Subsystem

The extraction subsystem 360 is shown here to comprise a singleextraction vessel 362, a solvent source vessel 364, and a liquid vessel366. The solids conduit 356 connects the separation vessel 348 and theextraction vessel 262 and is used to transport the solids from theseparation vessel 348 to the extraction vessel 362. The separationvessel 362 is connected to the solvent source vessel 364 via a solventconduit 368 having a solvent valve 370. The separation vessel 362 isalso connected to the liquid vessel 366 via a liquid conduit 372 havinga liquid valve 374. The separation vessel 262 is also includes a productconduit 376 having a product valve 378.

Recovery and Recycle Subsystem

The recovery and recycle subsystem 380 is shown here to comprise asingle a recovery and recycle vessel 382, a recycle formic acid vessel384, and a rare earth metal product vessel 386. The recovery and recyclevessel 382 is connected to the recycle formic acid vessel 384 via arecycle formic acid conduit 388 having a recycle formic acid valve 390.The recovery and recycle vessel 382 is connected to the rare earth metalproduct vessel 386 via a rare earth metal product conduit 392 having aproduct valve 394.

Fifth Embodiment

Referring now to FIGS. 4, a third embodiment of system of thisinvention, generally 400, is shown to include a commutating subsystem402, a reaction subsystem 416, a separation subsystem 438, an extractionsubsystem 454, and a recovery and recycle subsystem 476.

Commutating Subsystem

The commutating subsystem 402 includes a commutating unit 404 and amagnet source vessel 406. The magnet source vessel 406 is connected viaa magnet source conduit 408 having a magnetic source valve 410. Thecommutating unit 404 also includes a particulate magnet material conduit412 having a particulate magnet valve 414.

Reaction Subsystem

The reaction subsystem 416 includes a single reaction vessel 418, aformic acid source vessel 420, and a water source vessel 422. Thecommutating unit 404 is connected to the reaction vessel 404 via theparticulate magnet conduit 414. The formic acid source vessel 420 isconnected to the reaction vessel 418 via a formic aid conduit 424 havinga formic acid valve 426. The water source vessel 422 is connected to thereaction vessel 418 via a water conduit 428 having a water valve 430.The reaction subsystem 416 also includes a hydrogen gas utilization unit432 connected to the reaction vessel 418 via a hydrogen gas conduit 434having a hydrogen gas valve 436. The reaction subsystem 416 alsoincludes an inert gas source 438 connected to the reaction vessel 418via an inert gas conduit 440 having an inert gas valve 442. The reactionsubsystem 416 also includes a purge gas vent 444 connected to thereaction vessel 418 via a purge gas conduit 446 having a purge gas valve448. The reaction vessel 418 also includes a reaction mixture conduit450 having a reaction mixture valve 452.

Separation Subsystem

The separation subsystem 454 is shown here to comprise a singleseparation vessel 456 and a liquid receiving vessel 458. The reactionmixture conduit 450 connects the reaction vessel 418 and the separationvessel 456 and is used to transport the reaction mixture from thereaction vessel 418 to the separation vessel 454. The separation vessel456 is connected to the liquid receiving vessel 458 via a liquid conduit460 having a liquid valve 462. The separation vessel 456 also includes asolids conduit 464 having a solids valve 466.

Extraction Subsystem

The extraction subsystem 468 is shown here to comprise a singleextraction vessel 470, a solvent source vessel 472, and a liquid vessel474. The solids conduit 464 connects the separation vessel 456 and theextraction vessel 470 and is used to transport the solids from theseparation vessel 456 to the extraction vessel 470. The separationvessel 470 is connected to the solvent source vessel 472 via a solventconduit 476 having a solvent valve 477. The separation vessel 470 isalso connected to the liquid vessel 474 via a liquid conduit 478 havinga liquid valve 479. The separation vessel 470 also includes a productconduit 480 having a product valve 481.

Recovery and Recycle Subsystem

The recovery and recycle subsystem 482 is shown here to comprise asingle a recovery and recycle vessel 484, a recycle formic acid vessel486, and a rare earth metal product vessel 488. The product conduit 480connects the extraction vessel 470 to the recovery and recycle vessel484 and is used to transport the product to the recovery and recyclevessel 484. The recovery and recycle vessel 484 is connected to therecycle formic acid vessel 486 via a recycle formic acid conduit 490having a recycle formic acid valve 491. The recovery and recycle vessel488 is connected to the rare earth metal product vessel 488 via a rareearth metal product conduit 492 having a product valve 493.

Experiments of the Invention

The present invention is illustrated by the following examples:

The NdFeB magnets were obtained from discarded hard disk drives (HDDs).The HDDs were disassembled manually and 2 to 4 magnets were collectedfrom each HDD. Weights of the magnets ranged from about 2.5 g to about10 g. The NdFeB magnets used for the reactions were pretreated. However,the NdFeB magnets may be used as-removed without any pretreatment. Theterm “pretreatment” refers here to, but not limited to, demagnetization,roasting, and/or protective coating removal. The magnets were crushedinto small pieces using a metal crusher. The brittle magnets are easilybreakable into pieces, but any commutating method may be used includinggrinding, milling, crushing, external pressing, etc. The particle sizesvaried in a broad range between about 10 nm and about 5 mm. The crushedmagnet sample was reacted with a mixture of formic acid and water or anaqueous formic acid solution. In certain embodiments, the particle sizesrange between about 100 nm (0.1 {circle around (4)}m) to about 5 mm. Inother embodiments, the particle sizes range between about 500 nm (0.5{circle around (4)}m) to about 5 mm. In other embodiments, the particlesizes range between about 1 {circle around (4)}m to about 5 mm. In otherembodiments, the particle sizes range between about 5 {circle around(4)}m to about 5 mm. In other embodiments, the particle sizes rangebetween about 10 {circle around (4)}m to about 5 mm. In otherembodiments, the particle sizes range between about 100 {circle around(4)}m to about 5 mm. In other embodiments, the particle sizes rangebetween about 500 {circle around (4)}m to about 5 mm.

Example 1

As a first example of the process, a 1:2:2 w/w of magnet materials toformic acid to water reaction mixture was used for the reaction. Thereaction was performed at 100° C. for 24 h and the product was separatedby a filtration method at room temperature. The final product phase ofthe reaction was a white/pale violet microcrystalline precipitate whichwas confirmed to be a mixture of rare earth metal formate (REM(HCOO)₃)and iron formate dihydrate (Fe(HCOO)₂.2H₂O) phases from the powder X-raydiffraction techniques as shown in FIG. 5.

Several methods such as washing with different solvents, magneticseparation and density separation were attempted to remove the impureiron formate phase from the rare earth formate phase. The mostsuccessful route was to wash the precipitate with excess amounts ofwater. As per the PXRD data shown in FIG. 5, the final product afterexcess water washing contained only a pure REM(HCOO)₃ product,confirming successful recovery of rare earths from NdFeB magnetsmaterials.

When Fe²⁺ oxidizes to Fe³⁺, it forms nearly insoluble Fe(OH)₃, Fe(O)OH,and/or Fe₂O₃ phases. Thus, for a successful separation of Fe(HCOO).2H₂O,the iron formate phase needs to be fully removed. Any Fe(OH)₃ phase thatforms is hard to separate from the REM(HCOO)₃ phase, and thus remains asan impurity phase in the final product. REM(HCOO)₃ purity will besignificantly affected by Fe(OH)₃ formation, and is a previously knownproblem associated with the NdFeB magnet recycling techniques.

One alternative, is to carry out the final filtration step under aninert N2 atmosphere and using deoxygenated water for the washing steps.This was more successful compared to the regular filtration.

Example 2

In a further example, the amount of formic acid and amount of water andsolvent-to-solid ratios in the reaction mixture was systematicallyvaried, with the intention of exploiting the substantial solubilitydifference between Fe(HCOO).2H₂O and REM(HCOO)₃. Excess amounts of waterin the reaction mixture lowers the Fe(HCOO).2H₂O formationsignificantly, without affecting the REM(HCOO)₃ formation. When theamount of water increased substantially in the reaction mixture, theamount of Fe(HCOO).2H₂O was significantly reduced, or nearly absent fromthe final solid phase.

Based on the solubility data of Fe(HCOO).2H₂O, the required ratio ofmagnets to water to completely dissolve Fe(HCOO).2H₂O was calculated asabout 1:30 w/w magnet materials to water at 25° C. Thus, by adding theappropriate amounts of water to the reaction mixture, Fe(HCOO).2H₂Oformation can be substantially controlled. With this alteration of theprocess, the iron level in the final product was reduced between about0.5% and about 0.8%, and the rare earth purity level improved to 99% orabove.

Example 3

The detailed reaction scheme of the optimized process is as follows.

A ratio of magnet to formic acid was maintained at 1:2 w/w and a ratioof magnets to water was 1:30 w/w. Formic acid was used in a slightlyexcess amount over the theoretical amount to assist the reactioncompletion. The reaction temperature was set at 100° C.

The initial experiments were performed using 10 g of crushed magnets.The samples were mixed with 20 mL of 85% concentrated formic acid anddiluted with 300 mL of water. The reactions were performed in a roundbottom flask in an oil bath heated to 100° C. A vertically connectedLiebig condenser was attached to the flask neck to cool and condenseproduced vapor. The condenser was used to minimize loss of water andformic acid during the boiling. The open end of the condenser wasconnected to gas bubbler to monitor hydrogen gas (H₂) evolution duringthe reaction.

As the reaction progressed, the magnet pieces dissolved in the solutionand a white/greyish precipitate began to form and appear. Initialreactions were performed allowing 24 h reaction time to complete thereaction; subsequent experiments confirmed that within about 6 h ofreaction, all of the rare earth metals from the magnet samples weredissolved by the reaction mixture. Throughout the reaction period, theamount of the solid precipitate in the reaction mixture increased as theportion of dissolvable components of the magnets dissolved.

Afterward, the mixture was cooled to room temperature, about 25° C. andfiltered to separate the solid product from the liquid under suction.

Apart from the precipitate in the reaction mixture, parts of theprotective Ni/Cu coating of the magnets were found to have remainedunreacted with or undissolved by the formic acid/water mixture. Theseundissolved parts were easily removed using a magnetic stir barretriever, but any other type of magnetic separator may be usedincluding permanent or electromagnets or combination thereof. Theprecipitate was thoroughly washed with waster to remove any residual(Fe(HCOO)₂.2H₂O) adsorbed in the precipitate. The separation of anyresidual Fe(HCOO)₂.2H₂O from the product REM(HCOO)₃ may be achieved bywashing the precipitate with excess amounts of water as the two solidmaterials have substantial different solubility in water. Fe(HCOO)₂.2H₂Ois highly soluble in water, whereas the REM(HCOO)₃ is nearly insolublein water. Thus, by using an excess amount of water, the residualFe(HCOO)₂.2H₂O solid material can be completely removed from the solidproduct.

The white/greyish solid precipitate was confirmed as rare earth formate(REM(HCOO)₃). When an inadequate amount of water was used in thereaction, their formate dihydrate (Fe(HCOO)₂.2H₂O) phase may be observedin powder X-ray diffraction pattern.

After the removal of the residual Fe(HCOO)₂.2H₂O from the reactionmixture, the REM(HCOO)₃ phase was the only solid product remaining fromthe reaction mixtures. The final solid is dried under vacuum. The methodresulted in REM(HCOO)₃ being recovered in high yield of at least 90%.

As the final step, REM(HCOO)₃ is annealed at 750° C. for 3 h in air toobtain the mixture of rare earth oxides, REM₂O₃/REM₆O₁₁ (REM include Nd,Pr, Dy, Tb) with a recovered yield of at least 90% in a purity of atleast 99%. The purity of REM formate or oxides herein is measuredrelative to NREM formate or oxides in the relevant product.

The chemical analysis data of the final rare earth products phases haveshown that the methods of this invention are capable of recovering atleast 95% recovery efficiency for Nd, at least 95% recovery efficiencyfor Pr and at least 90% recovery efficiency for Dy and at least 85%recovery for efficiency for Tb.

The chemical analysis data of the final rare earth products phases haveshown that the methods of this invention are capable of recovering rareearth formates in greater than 90% purity, for example about 99% puritycompared to the non-rare earth formates.

REFERENCES CITED IN THE INVENTION

The following articles were cited above:

-   1. U.S. Department of Energy (2011) Critical Materials Strategy.-   2. Constantinides, S (2013) The Demand for Rare Earth Materials in    Permanent Magnets; Arnold Magnetic Technologies.-   3. U.S. Bureau of Mines (1993) Recycling of Neodymium Iron Boron    Magnet scrap.-   4. Xu X, Chumbley L S and Laabs F S (2000) Liquid metal extraction    of Nd from NdFeB magnet scrap. Journal of Materials Research 15(11):    2296-2304.-   5. Zakotnik M, Devlin E, Harris I R, and Williams A J (2006)    Hydrogen Decrepitation and Recycling of NdFeB-type Sintered Magnets.    Journal of Iron and Steel Research, International 13(1): 289-295.-   6. Itoh M, Miura K, and Machida K (2009) Novel rare earth recovery    process on Nd—Fe—B magnet scrap by selective chlorination using    NH4Cl. Journal of Alloys and Compounds 477: 484-487-   7. Samarasekere P, Wang X, Kaveevivitchai W, and Allan J.    Jacobson (2015) Reactions of Rare Earth Hydrated Nitrates and Oxides    with Formamide: Relevant to Recycling Rare Earth Metals. Crystal    Growth & Design 15(3):1119-1128-   8. Binnemans K, Jones P T, Blanpain B, Van Gerven T, Yang Y, Walton    A, and Buchert M (2013) Recycling of rare earths: a critical review.    Journal of Cleaner Production 51: 1-22 and references therein.-   9. Bolotovskii R L, Bolotovskii R L, Bulkin A p, Krutov G A, Turnov    V A, Ul'yanov V A, Anston O, Hiismaki P, Poyry H, Tittla A,    Loshmanov A A, and Furmanova N G (1990) Neutron diffraction study of    the crystal structure of rareearth and yttrium anhydrous deuterated    formates. Solid State Communications 76(8):1045-1049.

All references cited herein are incorporated by reference. Although theinvention has been disclosed with reference to its preferredembodiments, from reading this description those of skill in the art mayappreciate changes and modification that may be made which do not departfrom the scope and spirit of the invention as described above andclaimed hereafter.

1-10. (canceled)
 11. A system comprising: a reaction vessel including arare earth metal containing-magnet material input connect to a rareearth metal containing-magnet material source, a low molecular weightcarboxylic acid input connected to a low molecular weight carboxylicacid source, a water input connected to a water source, a waste liquidoutlet connected to a waste liquid receiver and a rare earth metalproduct outlet connected to a rare earth metal product receiver, wherean amount of the rare earth metal containing-magnet material, the lowmolecular weight carboxylic acid and the water are added to the reactionvessel to form a reaction mixture and the reaction mixture is held underreaction conditions sufficient to dissolve or extract the rare earthmetals to form rare earth metal carboxylates along with non-rare earthmetal carboxylate hydrates that precipitate out of the reaction mixture,and a separating vessel to separate the precipitate from the liquid andto wash the precipitate with a solvent to remove the non-rare earthmetal carboxylate hydrates to form a purified rare earth carboxylateproduct.
 12. The system of claim 11, further comprising: a commutatingunit to fragment the magnet material into a particulate magnet materialhaving an average particle size between about 10 nm and about 5 nm. 13.The system of claim 11, wherein the low molecular weight carboxylic acidis formic acid a magnet material to formic acid to water ratio isbetween about 1.0:1.0:20 w/w to about 1.0:2.0:50 w/w.
 14. The system ofclaim 13, wherein the magnet material to formic acid to water ratio isbetween about 1:1.2:20 w/w/ and about 1:1.8:50 w/w.
 15. The system ofclaim 14, wherein the magnet material to formic acid to water ratio isbetween about 1.0:1.4:20 w/w and about 1.0:1.5:40 w/w.
 16. The system ofclaim 15, wherein the magnet material to formic acid to water ratio isabout 1:1.44:30 w/w.
 17. The system of claim 11, wherein the reactionconditions include at least a reaction temperature, a reaction pressure,a reaction time, and a stirring rate.
 18. The system of claim 17,wherein: the reaction temperature is between about 25° C. and about 120°C., the reaction pressure is between about 1 atmosphere and about 5atmospheres, the reaction time is at least 24 hours, and the ratestirring is at least 500 rpm.
 19. The system of claim 18, wherein: thereaction temperature is any discrete temperature in the range betweenabout 25° C. and about 120° C., the pressure is ambient pressure, thereaction time is any discrete time period in the range between 3 hoursand 24 hours, and the stirring rates is any discrete stirring rate inthe range between 100 rpm and 500 rpm.
 20. (canceled)